Abrasive article



July 28, 1936. E STER 2,048,905

ABRASIVE ARTICLE Filed April 11, 1934 WITNESSES DUANE E.WEB6TER M W 8% W W Patented July 28, 1936 ABRASIVE ARTICLE Duane E. Webster, Worcester, Mass, assignor to Norton Company, Worcester, Mass, a corporation of Massachusetts Application April 11, 1934, Serial No. 720,090

2 Claims.

This invention relates to an abrasive article, and more particularly to a disk type of grinding wheel adapted to be mounted for grinding with a flat annular grinding face.

Certain types of grinding operations are most successfully accomplished by rapidly rotating the flat annular face of a grinding wheel in abrading engagement with the work. For example, one of the many common uses for a disk grinding wheel of this type comprises a dry grinding operation wherein the leaf of a metal spring, such as commonly employed in vehicles,

- is passed between two rapidly rotating abrasive disks so arranged that both of the opposed substantially flat faces of the spring leaf are ground simultaneously.

Heretofore, it has been the practice to imbed nuts or other suitable anchoring devices within recesses cut in the rear abrasive face of a grinding disk. These nuts are each secured in position by means of a cement or lead cast in position in the interstices between the nut and the grinding disk, thereby providing means whereby bolts may removably secure the grinding disk to a rotatable support. However, it has been found that grinding disks of this general type are not only expensive to manufacture, but are also expensive to use, due to the fact that the nuts or anchoring devices embedded in the abrasive prevent the entire abrasive wheel portion from being employed for a grinding operation. Consequently, the purchaser of such a grinding disk must pay for a considerable amount of abrasive material which cannot be employed for grinding and which must be discarded after the wheel has worn down to a certain thickness.

It has further been the practice to mount a solid disk shaped abrasive body on a rigid disk shaped iron plate by means of a cement and to removably secure the grinding unit to a rotatable support by means of ,bolts, passing through and secured to the plate, these clamping bolts being located within the central wheel hole. In view of the fact that many grinding disks of this type are especially intended for heavy duty grinding operations, the relatively small number of clamping bolts within the wheel hole, which are necessarily closely spaced to the wheel axis, must Withstand the heavy stresses and strains encountered in driving the grinding wheel during the grinding operation. In a construction of this type, the clamping bolts cannot be located at any great radial distance from the wheel axis, unless the wheel is made with an extra large hole and thereby providing less abrasive surface available for a grinding operation.

It is, therefore, the primary object of this invention to overcome the disadvantages of prior constructions and provide an inexpensive abrasive member construction including a rigid molded backing support integrally secured thereto and having anchoring devices embedded therein, whereby the abrasive member may be easily and removably secured to a suitable support for an abrading operation.

It is a further object of my invention to provide a grinding disk construction including an inexpensive, rigid, moulded backing support which is integrally secured thereto in such a manner that all of the abrasive material is available for an abrading operation, said backing support having widely spaced anchoring devices embedded therein whereby the disk may be evenly and removably clamped to a support for a grinding operation.

In accordance with the present invention, it is proposed to make an abrasive article, such as a grinding wheel adapted to grind with a flat, annular face, in the form of a laminated structure wherein a standard type of bonded abrasive body may be integrally and permanently secured to a molded, rigid backing support. Anchoring means such as nuts, studs or other suitable devices are embedded within the backing support at any desired locations during its manufacture, whereby the abrasive body and backing member may be easily and removably secured as a unit to any suitable support to perform a grinding operation. The backing support is integrally and permanently secured to the grinding wheel by means of an intermediate layer of rubber compound which is vulcanlzed in position therebetween and firmly adheres to both members, thereby providing a unitary structure.

In my preferred construction, the baclnng member is separately manufactured by any suitable molding operation with the anchoring dethe backing support and abrasive articles together as an inseparable unit.

One standard type of grinding wheel commonly referred to as a vitrified wheel may comprise abrasive grains, such as crystalline alumina or silicon carbide, bonded together into a suitable, coarse, rough surfaced, open pore structure by means of various types of ceramic materials such as are well known in the art. It will be appreciated that the strength of a grinding wheel of this general type is largely dependent upon the strength of the bond which secures the abrasive grains together.

In order to provide an integral grinding unit of sufficient strength to withstand heavy duty grinding operations without any tendency for the backing support to separate from the abrasive wheel, the backing support is preferably composed of such materials as will mold into a rigid member which of itself is stronger than the bonded abrasive wheel, and the intermediate layer of vulcanized rubber compound is preferably of such nature that it will form a tough, strong rubber bond which is at least as strong as the wheel bond and integrally unites the abrasive disk and backing support together as a permanent, inseparable unit.

Although this invention is particularly applicable to a vitrified type of abrasive body and means for removably securing it to-a support for performing a grinding operation, it will be appreciated that my invention applies equally well to other types of grinding wheels, such as silicate wheels or the so-called vitrified silicate wheels containing sodium silicate and other ingredients employed as bondingmedia and which are fired at a sufliciently high temperature to vitrify and form a strong wheel bond as is well recognized in the art. Furthermore, the present invention applies equally well to grinding wheels which employ a bond composed of. rubber.

In the case of a rubber bonded grinding wheel, or a molded hard rubber backing member, the intermediate layer of vulcanized rubber between the backing" member and the grinding wheel will serve to intimately unite with the rubber of the wheel bond or the rubber of the backing member during the vulcanizing operation. If a rubber backing member is secured to a rubber bonded grinding wheel in this manner, the structure will contain an intimately united rubber bond throughout its entire body. In other types of grinding wheels, the intermediate layer of rubber compound which securely grips the wheel to its backing member does not become integral with the wheel bond, but simply permeates the surface wheel pores to a suilicient extent to interlock therein and grip the wheel structure and backing member with sufficient tenacity to integrally secure them together as a unit. Since the rubber compound is forced into the wheel structure while in a soft, pliable condition, the penetration thereof may be controlled and regulated to such depth as is considered necessary for the purposes to which the grinding disk is to be employed.

In the drawing, which illustrates the preferred type of this invention, wherein like reference numerals indicate like parts:

Fig. 1 is a plan view of a grinding wheel embodying my invention which is partly broken away, and

Fig. 2 is a sectional view taken along the line 22 of Fig. 1.

In accordance with the preferred type of my invention, as illustrated, there has been provided a disk shaped grinding wheel H] of any desired thickness and diameter composed of abrasive grains, such as crystalline alumina or silicon carbide, suitably bonded together into a unitary grinding member. The bond may be a vitrified 5 ceramic material, in which case the abrasive body has open surface pores. If the wheel bond is rubber, the wheel face may be of low porosity. The wheel has a substantially fiat grinding face I2, a supporting face [4, and the respective inner and outer peripheral faces l6 and H. In order to suitably support the grinding wheel for a grinding operation, I employ a disk shaped backing member I8 adapted to be permanently and inseparably secured to the supporting face 14 of 15 the abrasive wheel ill as an integral unit therewith and arranged to be removably clamped to any suitable type of rotatable support. This rigid backing member may be composed of any suitable material which may be molded or otherwise 20 formed into a rigid wheel support. For example, this may comprise a disk shaped, hard rubber supporting member of the nature of ebonite or vulcanite or any of the various synthetic resinoids including phenolic condensation products 2 which are well'known in the art.

The backing member l8, which is preferably disk shaped, has two opposed substantially fiat faces 20 and 2| and inner and outer peripheral faces which respectively coincide with and corre- 30 spond to the wheel peripheries l6 and I1. Suitable anchoring members, which in the present instance are shown as hexagonal tapered anchoring nuts 23 having threaded portions, each of which terminates in a flat engaging surface 24, 35 are embedded within the molded backing member during the molding operation at predetermined locations with their surfaces 24 substantially even with the backing member face 2|, whereby suitable clamping devices such as bolts 26 may serve to removably secure the grinding unit to a rotatable support. Various other devices, such as bolts, studs, or other suitable members, may be embedded within the backing member I8 for this purpose and lie within the scope of my invention. One convenient type of support to which my grinding unit may be removably secured may comprise a disk shaped member 28 supported for rotation with a driving shaft 30 and having suit ably located holes 32 passing therethrough which are arranged to receive the clamping bolts 26. It is not deemed necessary to illustrate the rotatable support in detail, since it does not comprise part of this invention.

To permanently and integrally secure the backing member to the grinding wheel as a unit therewith, a layer of plastic vulcanizable raw rubber compound 35, which is preferably relatively thin as compared to the thickness of the backing member, is placed between the wheel and the backing 60 member in engagement with surfaces l4 and 20. This rubber compound contains a required amount of sulphur and, if desired, a vulcanization accelerator whereby the suitable application of heat and pressure will vulcanize it into either a hard or soft rubber which is strong and tough and which cements the grinding wheel to the backing member with sufficient tenacity to prevent their separation during a heavy duty grinding operation. If the rubber compound contains 5% or less of combined sulphur by weight, a soft rubber is formed and if more than 20% of sulphur is present, a hard rubber of the nature of ebonite or vulcanite is formed.

In the construction of the preferred type of my invention, the backing member 58 is separately manufactured in any suitable manner, as by any suitable molding operation well brown to the art.- During the manufacture of this backing member, the clamping nuts 23 or other suitable clamping devices are located and permanently embedded therein in such a manner as to be secured at predetermined locations as integral parts of said member. In the present illustrations, the clamping nuts are so positioned that their faces 24 are substantially even with the face 2! of the backing member and the tapering faces of said nuts converge towards face 2!. It will thus be appreciated that in such a construction, the nuts will be firmly secured in position and will not tend to pull loose from the backing member.

If the backing member comprises other materials than hard rubber, the supporting surface 20 is preferably roughened in any well-known manner to aid the vulcanized rubber 35 in adhering thereto. If desired, surface 20 of the backing member may be provided with suitable channels, or grooves, or reentrant holes may pass through the backing member to aid the rubber to firmly grip thereto. In any event, regardless of the material of which the backing member is composed, the backing member first has its supporting face 20 thoroughly cleaned and then a layer of raw plastic rubber compound 35 of desired thickness and containing the required amount of sulphur and, if desired, a suitable vulcanization accelerator, is placed upon surface 20. The grinding wheel ID is then placed on the rubber sheet 35 and suflicient pressure applied in any suitable manner to cause the raw plastic rubber to deform and flow into the open pore structure of wheel face It to the desired depth and embrace the roughened surface portion of the wheel. While the rubber compound is thus compressed, sufilcient heat, such as 200 to 250 C.,' is applied to vulcanize the rubber in position and.

cause it to firmly adhere to both the wheel and backing member, thereby permanently securing them together as an integral unit capable of withstanding the stresses and strains of a heavy duty grinding operation. By applying various pressures during the vulcanization process, the layer of raw plastic rubber may impregnate the grinding wheel for any required amount and be vulcanized in position, thereby securing the wheel to the backing plate with any desired tenacity.

It will be appreciated that a grinding wheel as' disclosed in my invention is very economical, since it may be used until substantially all of the abrasive is worn away. If desired, after the grinding wheel has been worn away, another grinding wheel may be secured to the backing member by the same method as heretofore described. However, due to the low cost of my type of backing member, it is usually discarded when the abrasive wheel has been worn away and a new grinding unit is purchased, thus making it unnecessary to ship the backing member to the factory and have a new wheel installed thereon.

Although I have described in my preferred method of construction one means of securing a separately manufactured backing member to a grinding wheel by vulcanization, it will be appreciated that it may not be necessary to separately manufacture the backing member. For example, if a hard rubber backing member were to be employed, the grinding wheel ill could be placed upon a layer of suitable plastic raw rubber compound containing sulfur which is of such composition that it would vulcanize to form a hard rubber back i8 as described. The nuts 23 could be embedded in the rubber compound while plastic. Application of suitable heat and pressure thereafter would cause the rubber compound to flow into the surface wheel pores and vulcanize in position without necessitating any intermediate layer of vulcanizable rubber compound, as illustrated in my preferred construction.

.While I have specifically described my invention as particularly adaptable to the manufacture of an abrasive wheel and a method of securing it to a rigid backing support, it will be apparent to those skilled in the art that various other abrasive articles may be easily mounted in grinding position in the same manner. For example, a bonded abrasive body having a suitable abrading surface and commonly referred to as a rubbing block may be permanently cemented to a molded organic backing member in the same manner as employed in my preferred type of grinding wheel construction, and suitable anchoring' devices may be embedded in-the backing member to receive clamping devices, such as bolt or screws, whereby the unit may be easily and removably secured to any suitable support. Such modifications or substitutions of my invention as lie within the scope of the appended claims are to be considered as embodied in the above specification.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is: r

1. A grinding wheel comprising a disk shaped annular body of bonded abrasive grains having a substantially flat grinding face, a rigid hard rubber backing therefor which is vulcanized to the abrasive bodyand forms an integral unit therewith, and means including anchoring devices embedded within the backing whereby the entire unit may be demountably secured in position.

2. A grinding wheel comprising a disk shaped annular body of bonded abrasive grainshaving a substantially flat grinding face, a separately manufactured, rigid, hard rubber backing member therefor having widely spaced anchoring devices embedded therein at predetermined locations, an intermediate layer of rubber compound vulcanized in position and permanently securing the abrasive body and backing member together 

